1. Technical Field
The present invention relates to, for example, a MEMS (Micro Electro Mechanical Systems) device in which a functional element, such as a resonator, a sensor and an actuator, and/or an electronic circuit are integrated on one substrate, and a method of manufacturing such a MEMS device.
2. Related Art
For example, in a MEMS device that includes a resonator with capacitance as a functional element, the resonator is airtightly sealed, in a vacuum state, in a cavity formed in a substrate. Also, even in the case of a functional element that does not require airtight vacuum seal, the functional element is airtightly sealed in a cavity so as to prevent the influences of dust, moisture, and the like.
Traditionally, in a case where such a functional element and a semiconductor circuit element are integrated on one semiconductor substrate, a cavity is formed by providing the functional element on the semiconductor substrate and surrounding the functional element with an insulating film and the like. Therefore, the cavity obstructs formation of wiring on the semiconductor substrate via an insulating layer.
In such a MEMS device, a special process, such as wire bonding or TSV (Through Silicon Via), is used to electrically connect the functional element to the semiconductor circuit element. In an alternative case where connection can be realized using a standard semiconductor wafer process, an enormous restriction is imposed on routing of wiring for electrically connecting the functional element to the semiconductor circuit element. As a result, electrical connection between the functional element and the semiconductor circuit element becomes complicated, thereby triggering a decrease in a degree of freedom of design of the MEMS device and an increase in cost.
As a related technique, JP-A-2008-100325 (paragraphs 0004 to 0006, FIG. 8) discloses a MEMS and semiconductor composite circuit that realizes a structure which facilitates planarization of a layer structure provided on a semiconductor substrate, and which is resistant to the inter-influences between an element structure of a semiconductor element portion and a MEMS structural member. In this MEMS and semiconductor composite circuit, a MEMS trench structure and a boundary trench structure are formed in a surface layer portion of a semiconductor substrate. The MEMS trench structure is composed of a surface recessed portion for achieving element isolation for a MEMS structural member with respect to the semiconductor substrate, and an insulating member installed inside the surface recessed portion. The boundary trench structure is composed of a surface groove that is provided in an element boundary portion for achieving element isolation for a semiconductor element portion, and an insulating member installed inside the surface groove. A surface of the insulating member in the MEMS trench structure is constructed to be lower than a substrate surface of the semiconductor substrate, and the MEMS structural member is formed on the surface of the insulating member.
On the other hand, JP-T-2009-516346 (abstract, claim 9, FIG. 1) discloses an electronic device that has a MEMS element in a cavity. This electronic device has a substrate of a semiconductor material with a first side and an opposite second side, and a MEMS element which is provided with a fixed electrode and a movable electrode. The movable electrode is formed in a closed cavity and is movable towards and from the fixed electrode between a first gapped position and a second position. The cavity is opened through etching holes in the substrate that are exposed on the second side of the substrate, the electrodes are coupled to contact pads on the first side, and a resin layer is present between the electrodes of the MEMS element and the contact pads. The substrate is provided with a packaging portion on the second side through which the etching holes extend, and the cavity is at least partially present between the movable electrode and the packaging portion.
JP-A-2008-100325 (paragraphs 0004 to 0006, FIG. 8) and JP-T-2009-516346 (abstract, claim 9, FIG. 1) are examples of related art.
JP-A-2008-100325 (paragraphs 0004 to 0006, FIG. 8) and JP-T-2009-516346 (abstract, claim 9, FIG. 1) disclose formation of a MEMS trench structure and a cavity in a semiconductor substrate, and provision of a MEMS element in the cavity. However, as the MEMS element extends in a region that is higher than a main surface of the substrate, a part of the cavity surrounding the MEMS element is formed in the region that is higher than the main surface of the substrate, thereby obstructing formation of wiring on the substrate via an insulating layer.